Transparent LED displays are rapidly gaining popularity. However, these screens will never achieve the level of transparency that can be achieved with COB.
With current SMD technology the LEDs are place on top of each PCB strip. This interferes with the degree of transparency.
COB integrates the chip in the PCB strip itself.
Click here to compare the drawing above with SMD and COB.
Click here for a short video of a transparent SMD screen in Paris.